Proton Therapy Treatment Monitoring: Prompt Gamma Emission Reconstruction in the Time and Space Domain

Prompt Gamma Timing is a technique proposed for range monitoring in proton therapy. The experimental measurements so far are limited to a single secondary proton detector. In this study we present an innovative technique to merge the information from many detectors in different positions into a unique estimation of the beam particle motion in the spatiotemporal domain. We test the proposed method by means of Monte Carlo simulations, with various beam ranges and a number of primaries interesting for proton therapy monitoring (10 ⁷ ). The method is based on the Maximum Likelihood Expectation Maximization algorithm, and we show its applicability with both MeV-range gamma detectors as well as lower energy detectors such as PET detectors. The preliminary results shown indicate a range resolution of about 5 mm. The ultimate goal of this study is to provide a robust mathematical instrument to expand the significance of Prompt Gamma Timing measurements, to be useful for the prototypes presently under construction by the treatment monitoring community.